JP-2004-29871 teaches a traffic information system including an information center and an in-vehicle device. The information center estimates and analyzes a traffic condition based on traffic information transmitted from a probe vehicle. The probe vehicle as an information gathering, vehicle collects the traffic information regarding a road, on which the probe vehicle runs. The in-vehicle device displays the traffic condition on a display device based on the traffic information transmitted from the information center.
In the above system, the traffic information regarding only the road, on which the probe vehicle actually drives, is gathered in the center. The center estimates the traffic condition about the road based on the gathered traffic information, and distributes the estimated traffic condition.
Accordingly, regarding a section of a road, on which the probe vehicle does not run, or the probe vehicle seldom runs, the center cannot estimate the traffic condition of the section of the road with high accuracy. Accordingly, when the in-vehicle device searches an optimum route so, as to avoid a traffic jam based on the traffic condition distributed from the center, the optimum route may include the section of the road, on which the probe vehicle does not run, or the probe vehicle seldom runs. In this case, the in-vehicle device guides the optimum route including the section of the road, on which the probe vehicle does not run, or the probe vehicle seldom runs.
Thus, it is required for in-vehicle device to search the optimum route not including the section of the road, on which the probe vehicle does not run, or the probe vehicle seldom runs.